Offset Line-Vertical offset: BROKEN?!

I don’t know if I’m having a brain f*rt or my TBC is broken. Someone please offset (TBC OFFSETLINE) the attached linestring 10’ right at 0% and do an Explore Object referencing the new line checking the resulting cross slope and let me know what your getting. I am NOT getting 0% for the entire length as expected. It appears that, due to the arcs, it’s not calc’ing the Z value radially resulting in wildly erroneous results.

Moving on using Vertical Design as that appears to be calc’ing correctly, however, if others are seeing what I am seeing with the simple command, Trimble needs to release a patch immediately.

not 0%

Centerline.vcl (150.4 KB)

Yeah its not calcing something correct.

Thanks Eric
I was starting to question my math’ing for a hot minute.

The response from Trimble is that it is not a bug - they are saying that computing an offset line where the source lines have variable elevations is tricky because the offset line has a different length to the source line and depending on the distribution of elevations along the source line you can create varying effects on the elevations and therefore cross slopes to the offset line.

This is where slope designer comes in - have you tried that? It will compute points along the source line and then determine the offsets and slopes at all those locations to give a better result in this scenario I ran the test on the alignment provided and everywhere I checked the surface created using the HAL and the Slope Designer Line has a 0% cross slope whereas the surface between the HAL and the Offset line does not have a 0% cross slope.

We spent a lot of time on this in the development of Slope Designer for these exact reasons to create a tool that handles all of the cross slope scenarios in a extremely robust manner.

Offset line basically computes elevations on the offset line at points where VPIs exist in the source line and then interpolates between them, whereas slope designer computes many points along the source line nd then applies the cross slope from those computed points - thereby giving a better result in all situations.

Take a look at the project file here

Alan

3 Likes

Ok thanks Alan. Slope Designer is on my ever expanding list of things to figure out. That and 0 does not equal 0 I guess.